"Theresa May has decided to ally herself with Donald Trump's bigoted, misogynistic government. She has refused to speak out against Donald Trump's #MuslimBan - even when her own Members of Parliament are targeted. It is not only weak, it is a matter of national shame - disgracing our country across the world. "There are moments of terrible injustice throughout history where we look back and rightly ask - what did people do? Future generations will look back at the targeting of Muslims - as we look back at the targeting of Jews - with disgust, horror and shame. If we do not speak out, we are complicit. "Theresa May has betrayed her own people. That doesn't mean we have to. Let's stand in solidarity with those targeted by Donald Trump's hateful government, including the people of this country, outside Downing Street and all over Britain."

This is how the protest shaped up at the start (as filmed by Business Insider at the beginning of the demonstration):

The protest was meant to start at 6 p.m. GMT (1 p.m. ET) but by 5 p.m. GMT thousands had already gathered outside the official residence of Prime Minister Theresa May.

Donald Sinclair for Business Insider

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The pavements were spilling over with people on their way to the protest too.

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Police had already erected barriers and were monitoring the crowds.

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People were loaded with signs and banners expressing strong criticism over the US President's executive order.

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In Britain, more than a million people have petitioned for Trump's planned state visit to the UK to be cancelled. However, Theresa May insisted the visit would still go ahead, no matter how many people signed a petition against it.

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Meanwhile some protestors were there to show support for the LGBTQA (Lesbian, Gay, Bisexual, Transgendered, Questioning, and Allied) community. One of the chants about Trump also incorporated a famous catchphrase from the show "Ru Paul's Drag Race" — "Immigrants, shantay you stay. Trump, sashay away"

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Some of the traffic lights even had a symbol of support for the LGBTQA community — a stencil of a same-sex couple on the green light.

Donald Sinclair for Business Insider

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And here is another.

Donald Sinclair for Business Insider

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There were some more humorous signs too, including this one in Scottish slang saying: "State visit? We say you canny ya big orange fanny."

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In Scotland, the same sense of humour is on other signs, such as this one ...

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... and this crude, yet poignant one.

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And here is a short video showing the protest crowd and chants growing in size and volume.

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And here is another video of a chant: "Hey hey, ho ho, Trump and Brexit's got to go."

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Around 20 prominent speakers were said to be attending the event on Monday evening.

By 6:30 p.m. GMT, the crowds swelled to such a level, they poured onto the walls and onto the steps of buildings lining the street.

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By 6:40 p.m. GMT, nearby Trafalgar Square was flooded with protestors and police.

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By 6:50 p.m. GMT, more people had finished work and were still heading to Downing Street to attend the protest.

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At 7 p.m. GMT, Angus Robertson is MP for Moray, Westminster SNP Leader and Deputy Leader of the Scottish National Party spoke at the event amid chants of "no state visit."

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Meanwhile, protests grew in other major cities across Britain, including Glasgow, Scotland ...

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... Leeds, England ...

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... Newcastle in the north of England ...

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... as well as the affluent city of Cambridge, where one of the world's most prestigious universities resides.

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Meanwhile, as of 7:20 p.m., 10 Downing Street and Trafalgar Square became completely flooded with people.

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People's signs related Trump's administration to the dystopian future presented in George Orwell's classic novel "Nineteen Eighty-Four," as well as the President as the fictional antagonist from the Harry Potter series Lord Voldemort.

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As more and more people turned up into the evening, placards and banners criticising Prime Minister May's "special relationship" with Trump was parodied.

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That is because the protest was not just about Trump's immigration ban — it was about May's supposed complicity in it, by not condemning the move. The organisers in the event info said: "Theresa May has decided to ally herself with Donald Trump's bigoted, misogynistic government. She has refused to speak out against Donald Trump's #MuslimBan - even when her own Members of Parliament are targeted."

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As it hit the half way point for the scheduled demonstration at 8 p.m. GMT, the streets fill up to the edges of the Thames river. In the near distance, you can see the London Eye.

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And the crowds outside the PM's front door were immense.

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During the long night ahead, protestors found time to sit down occasionally ...

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... because even trying to travel from the nearby Westminster tube station was a logistical nightmare.

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As it reaches past 9 p.m. GMT former Minister of Faith and Communities Baroness Sayeeda Warsi (C) was spotted addressing the crowd during the protest.

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Shadow Attorney General Baroness Shami Chakrabarti was also spotted addressing the crowds.

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One of the themes running through the banners at the protest was reference to Neville Chamberlain — the former Conservative UK Prime Minister from 1937 to May 1940 whose "appeasement" policy towards Adolf Hitler was said to have helped his eventual rise to power. #TheresaTheAppeaser was trending on Twitter during the evening.

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While the protest is meant to end around 10 p.m. GMT, it was still going strong and it looked like the crowds would not disperse any time soon.